Current practices and challenges of outpatient parenteral antimicrobial therapy: a narrative review

Extended hospitalization for infection management increases inpatient care costs and the risk of healthcare-associated adverse events, including infections. The growing global demand for healthcare, the diminishing availability of hospital beds and an increasing patient preference for care within their own home have been the primary drivers of the expansion of hospital-in-the-home programmes. Such programmes include the use of IV antimicrobials in outpatient settings, known as outpatient parenteral antimicrobial therapy (OPAT). However, OPAT practices vary globally. This review article aims to describe the current OPAT practices and challenges worldwide. OPAT practice begins with patient evaluation and selection using eligibility criteria, which requires collaboration between the interdisciplinary OPAT team, patients and caregivers. Depending on care requirements, eligible patients may be enrolled to various models of care, receiving medication by healthcare professionals at outpatient infusion centres, hospital clinics, home visits or through self-administration. OPAT can be used for the management of many infections where an effective oral treatment option is lacking. Various classes of parenteral antimicrobials, including β-lactams, aminoglycosides, glycopeptides, fluoroquinolones and antifungals such as echinocandins, are used globally in OPAT practice. Despite its benefits, OPAT has numerous challenges, including complications from medication administration devices, antimicrobial side effects, monitoring requirements, antimicrobial instability, patient non-adherence, patient OPAT rejection, and challenges related to OPAT team structure and administration, all of which impact its outcome. A negative outcome could include unplanned hospital readmission. Future research should focus on mitigating these challenges to enable optimization of the OPAT service and thereby maximize the documented benefits for the healthcare system, patients and healthcare providers.

Stability of intravenous medicines - evidence of maximum temperature reached in both summer and winter within soft shell elastomeric pumps

OBJECTIVE

Elastomeric devices or pumps are a valuable tool to deliver outpatient parenteral therapy and have been used for administration of chemotherapy, antibiotics and pain medication. A key determinant of effective treatment is to consider the stability of medicines within these devices. It is widely known that an increase in temperature positively correlates to an increase in drug degradation. The objective of our work was to measure the temperature within soft shell elastomeric devices, under simulated outpatient treatment conditions in summer and winter months, and to determine the maximum temperature reached within these periods of use.

METHODS

Thermocouples were inserted within soft shell Easypump II (B Braun Medical, Sheffield, UK) elastomeric pumps and the temperature was monitored under simulated outpatient conditions during cold and warm weather with different fill volumes. Temperature monitoring was also conducted with varying levels of insulation around the devices.

RESULTS

Our results show that internal temperatures remained below 32°C±1°C in winter and summer months, including during times defined as a heatwave. Fill volume and ambient temperature were shown to be significant factors affecting the internal temperatures reached.

CONCLUSION

A soft shell Easypump II elastomeric pump, if used within its carry pouch, will maintain the internal solution below a temperature of 32°C±1°C if patients correctly adhere to handling guidance. Our results show that further improvements to the insulation material used in carry pouches can significantly restrict the rate of temperature rise within the pumps and will give more assurance in relation to preventing degradation especially considering the increases in extreme weather conditions observed in recent years due to global warming.

Outpatient parenteral antimicrobial therapy (OPAT) across the world: a comparative analysis-what lessons can we learn?

This paper presents a comparative analysis of Outpatient Parenteral Antimicrobial Therapy (OPAT) structures and delivery options across different countries. OPAT, a cost-effective alternative to inpatient care for patients requiring IV antimicrobial therapy, has demonstrated multiple benefits such as patient satisfaction, economic cost savings, and reduced hospital-acquired infections. Despite these advantages, there is considerable international variation in OPAT use and implementation. By examining the OPAT structures of multiple countries, we aim to identify areas of variation and explore opportunities for expansion and improvement of OPAT services.

Making a case for outpatient parenteral antimicrobial therapy (OPAT)

In the wake of the COVID-19 pandemic, and its negative impact on both acute and elective care and decline in available inpatient resources, there is an imperative to maximize safe and effective alternatives to inpatient hospital care. Properly governed outpatient parenteral antimicrobial therapy (OPAT) services embed the principles of antimicrobial stewardship (AMS) (including use of early oral therapy) and support admission avoidance and early discharge for a growing range of patient groups with complex infections through well-organized multidisciplinary team working. Expansion of OPAT aligns with the UK's national strategy to deliver care closer to home and cost-effectively maximize use of inpatient resources. OPAT serves as an exemplar to other ambulatory services and presents opportunities for developing and assuring AMS strategies within the rapidly developing hospital-at-home and virtual ward environments.

Outpatient parenteral antimicrobial therapy (OPAT) in Germany: insights and clinical outcomes from the K-APAT cohort study

PURPOSE

Outpatient parenteral antimicrobial therapy (OPAT) offers several key advantages, including enhanced patient quality of life, reduced healthcare costs, and a potential reduction of nosocomial infections. It is acknowledged for its safety and effectiveness. This study provides the first systematic clinical data for Germany, where OPAT has not yet been widely adopted. The aim is to establish a foundational reference point for further research and integration of OPAT into the German healthcare system.

METHODS

This prospective observational study descriptively analyses data obtained from a cohort of patients receiving OPAT. Both in- and outpatients from all medical specialties could be recruited. Patients administered the anti-infective medications themselves at home using elastomeric pumps.

RESULTS

77 patients received OPAT, with a median duration of 15 days and saving 1782 inpatient days. The most frequently treated entities were orthopaedic infections (n = 20, 26%), S. aureus bloodstream infection (n = 16, 21%) and infectious endocarditis (n = 11, 14%). The most frequently applied drugs were flucloxacillin (n = 18, 23%), penicillin G (n = 13, 17%) and ceftriaxone (n = 10; 13%). Only 5% of patients (n = 4) reported to have missed more than one outpatient dose (max. 3 per patient). Only one catheter-related adverse event required medical intervention, and there were no catheter-related infections.

CONCLUSION

The study demonstrates that OPAT can be safely conducted in Germany. In preparation for its broader implementation, crucial next steps include creating medical guidelines, fostering interdisciplinary and inter-sectoral communication, as well as creating financial and structural regulations that facilitate and encourage the adoption of OPAT.

TRIAL REGISTRATION NUMBER

NCT04002453.

Home nursing and self-administered outpatient parenteral antimicrobial treatment: a comparison of demographics and outcomes from a large regional hospital in Queensland, Australia

BACKGROUND

Outpatient parenteral antimicrobial treatment (OPAT) is a safe and effective therapy used in several settings across Australia. As OPAT services expand their inclusion criteria to include complex patient populations, there is an increased need for selecting appropriate patients to receive either healthcare-administered OPAT (H-OPAT) or self-administered OPAT (S-OPAT).

AIMS

To describe patient demographics, diagnosis, microbiology and outcomes of patients treated by H-OPAT and S-OPAT within the Sunshine Coast Hospital and Health Service, Australia.

METHODS

Data on demographics, diagnoses, treatment and outcomes on all patients treated by H-OPAT and S-OPAT from March 2017 to December 2019 were collected retrospectively.

RESULTS

One hundred and sixty-five patients (62.26%) were enrolled in H-OPAT and 100 patients (37.74%) in S-OPAT. S-OPAT patients were significantly younger. H-OPAT patients were more comorbid. Bone and joint infections were the most treated infections and were more likely to be treated by S-OPAT. There was no difference in treatment duration, cure and complication rates between S-OPAT and H-OPAT. Longer duration of therapy was associated with more complications. Treatment failure was associated with infections due to multiple organisms, number of comorbidities and treatment of surgical site, skin and soft tissue infections.

CONCLUSIONS

There were significant differences in demographics between H-OPAT and S-OPAT without any difference in outcomes. Overall failure and complication rates were low. Higher rates of treatment failure were predicted by the diagnosis, number of comorbidities and number of organisms treated.

Guidelines to practice in hospitals at home: safe and effective continuous infusion pumps substantially increased penicillin use in erysipelas treatment

Hospitals at home are increasingly offering outpatient parenteral antimicrobial therapy (OPAT) in an attempt to reduce costly inpatient care, but these settings favour broad-spectrum antibiotics that require less frequent dosing than penicillin. Benzyl penicillin could be delivered via continuous infusion pumps (eCIPs), but studies on their safety and efficacy in OPAT are scarce, and it remains unclear how much the availability of eCIPs increases penicillin use in real-life settings. We examined 462 electronic healthcare records of erysipelas patients treated between January 2018 and January 2022 in a large Finnish OPAT clinic. Average marginal effects from logistic models were estimated to assess how the introduction of eCIPs in December 2020 affected penicillin use and to compare clinical outcomes between patients with and without eCIPs. Introduction of eCIPs increased the predicted probability of penicillin treatment by 36.0 percentage points (95% confidence interval 25.5-46.5). During eCIP implementation, patients who received an eCIP had 73.1 (58.0-88.2) percentage points higher probability than patients without an eCIP to receive penicillin treatment. They also had about 20 percentage points higher probability to be cured at the time of discharge and 3 months after it. Patient and nurse satisfaction regarding eCIPs was very high. Benzyl penicillin eCIP treatment is effective and safe, and substantially increases the use of penicillin instead of broad-spectrum antibiotics. To reduce the risk of antimicrobial resistance, eCIPs could increasingly be promoted for use in OPAT clinics, and there should be adequate education and support in their implementation.

A Qualitative Review of Patient Feedback for the OPAT (Outpatient Antimicrobial Therapy) Service in Bristol

Outpatient parenteral antimicrobial therapy (OPAT) aims to deliver intravenous antimicrobials to medically stable patients with complex infections outside of a hospital setting. There is good evidence to demonstrate the safety and efficacy of OPAT in the literature. Anecdotally, the feedback from patients has been positive, but only a few studies evaluate this topic in detail. The aim of this qualitative study was to examine patients' experiences with and feedback on the OPAT service in Bristol, United Kingdom, which was established in 2021. A total of 92 patient feedback surveys were reviewed retrospectively, and thematic analysis was undertaken. Feedback from OPAT patients in our centre was overwhelmingly positive. The key themes identified were benefits to the patients, their friends, and family, and positive feedback about OPAT staff. The mean overall satisfaction score for OPAT was 9.6 out of 10. Areas to improve included communication between the OPAT and parent teams, improving OPAT capacity, and expansion of the service.

Outpatient parenteral antibiotic treatment for infective endocarditis: A retrospective observational evaluation

BACKGROUND

Infective endocarditis (IE) requires long courses of intravenous (IV) antibiotics. Outpatient parenteral antibiotic therapy (OPAT) saves resources, improves the patient experience and allows care in their preferred place; however, questions remain about safety when treating IE patients. This study evaluates OPAT management of IE patients in our region between 2006 and 2019.

METHODS

This is a retrospective observational evaluation and description of outcomes and adherence to suitability criteria, according to British Society for Antimicrobial Chemotherapy (BSAC) guidelines.

RESULTS

We identified five models of OPAT delivery. The number of patients treated expanded significantly over time. Of 101 patients, six (6%) suffered poor outcomes, but each patient had contributing factors outside of the primary infection. Median OPAT duration was 12 days and 1,489 hospital bed days were saved.

CONCLUSIONS

In a setting where there was good adherence to BSAC criteria, treating IE patients using OPAT services was safe. Complications observed were likely independent of treatment location. Significant bed days were saved.

Barriers and facilitators for the implementation and expansion of outpatient parenteral antimicrobial therapy: a systematic review

Outpatient parenteral antimicrobial therapy (OPAT) has been expanding in recent years and serves as a viable solution in reducing the shortage of hospital beds. However, the wider implementation of OPAT faces numerous challenges. This review aimed to assess implementation barriers and facilitators of OPAT services. Studies describing barriers and facilitators of the OPAT service were retrieved from PubMed, Scopus, MEDLINE, EMBASE, CINAHL, Cochrane Library, Web of Science Proceedings, International Pharmaceutical Abstracts and PsycINFO. All types of study designs published in the English language were included. Studies that did not mention any barrier or facilitator, did not differentiate OPAT and inpatient, focused on specific antimicrobials or diseases, and made no distinction between parenteral and other treatments were excluded. Qualitative analysis was performed using the 'best-fit' framework approach and the Consolidated Framework for Implementation Research (CFIR). The review was PROSPERO registered (CRD42023441083). A total of 8761 studies were screened for eligibility and 147 studies were included. Problems in patient selection, lack of awareness, poor communication and co-ordination, lack of support, lack of structured service and inappropriate prescriptions were identified. OPAT provides safe, effective and efficient treatment while maintaining patients' privacy and comfort, resulting in less daily life disruption, and reducing the risk of infection. Satisfaction and preference for OPAT were very high. Initiatives in strengthening OPAT such as antimicrobial stewardship and telemedicine are beneficial. Challenges to and facilitators of OPAT were identified among patients, health professionals, OPAT service providers and healthcare administrators. Understanding them is crucial to designing targeted initiatives for successful OPAT service implementation.

Creation and Validation of an Automated Registry for Outpatient Parenteral Antibiotics

Existing outpatient parenteral antibiotic therapy (OPAT) registries are resource intensive, and OPAT programs struggle to produce objective data to show the value of their work. We describe the building and validation of an automated OPAT registry within our electronic medical record and provide objective data on the value of the program. Variables and outcomes include age, sex, race, ethnicity, primary insurance payor, antibiotic names, infection syndromes treated, discharge disposition, 30-day all-cause readmission and death rates, complications, and an estimate of the hospital days saved. Records for 146 OPAT episodes were reviewed manually to validate the registry. Data were displayed in a dashboard within the electronic medical record. Over the 4-year time frame, our registry collected 3956 unique patients who completed 4710 episodes (approximately 1200 episodes per year). A total of 400 complications during OPAT were identified. All variables had an accuracy of >90% on validation. The OPAT program resulted in a reduction in hospital length of stay by 88 820 days, or roughly 22 000 days per year. We intend our registry to serve as a blueprint for similar OPAT programs with limited administrative resources. Wider application of our system would allow for easier aggregation and comparisons of OPAT practice and address the lack interinstitutional standardization of OPAT data and outcomes.

Personalising intravenous to oral antibiotic switch decision making through fair interpretable machine learning

Antimicrobial resistance (AMR) and healthcare associated infections pose a significant threat globally. One key prevention strategy is to follow antimicrobial stewardship practices, in particular, to maximise targeted oral therapy and reduce the use of indwelling vascular devices for intravenous (IV) administration. Appreciating when an individual patient can switch from IV to oral antibiotic treatment is often non-trivial and not standardised. To tackle this problem we created a machine learning model to predict when a patient could switch based on routinely collected clinical parameters. 10,362 unique intensive care unit stays were extracted and two informative feature sets identified. Our best model achieved a mean AUROC of 0.80 (SD 0.01) on the hold-out set while not being biased to individuals protected characteristics. Interpretability methodologies were employed to create clinically useful visual explanations. In summary, our model provides individualised, fair, and interpretable predictions for when a patient could switch from IV-to-oral antibiotic treatment. Prospectively evaluation of safety and efficacy is needed before such technology can be applied clinically.

Systematic review of room temperature stability of key beta-lactam antibiotics for extended infusions in inpatient settings

BACKGROUND

Extended infusion (EI) of beta-lactam antibiotics may offer clinical benefits aligned with improved probability of target attainment for critical pharmacokinetic/pharmacodynamic parameters that correlate with efficacy. There is much research interest in prolonged and continuous infusions (collectively, extended infusions) of beta-lactams to improve patient outcomes, particularly in critically ill patients in intensive care. While definitive clinical trial data demonstrating beneficial outcomes is awaited, there has been limited focus on the stability of the agents given by EI, which may be an equally critical parameter. EI may allow for savings in nursing time due to reduced need for drug reconstitution. We set out to examine the data for stability for EI at room temperature, consistent with the requirements of 'A Standard Protocol for Deriving and Assessment of Stability- Part 1 Aseptic Preparation (Small Molecules)', which allows a 5% loss of active pharmaceutical ingredient (API) applicable for those territories that use the British Pharmacopoeia also for a 10% loss applicable in much of rest of the world.

METHODS

Searches using preferred reporting items for systematic reviews and meta-analyses (PRISMA) principles for stability data on freshly prepared beta-lactam antimicrobials for extended administration at room temperature (at or above 23°C) were conducted in November 2021 and updated in December 2022.

RESULTS

We found data to support the extension of the shelf life of 12 key beta-lactam antibiotics once reconstituted (aztreonam, amoxicillin, benzylpenicillin, flucloxacillin, piperacillin/tazobactam, cefazolin, cefmetazole, ceftaroline, ceftazidime, ceftriaxone, imipenem and meropenem) compliant with the NHS protocol, and data for five other agents (ticarcillin, cefepime, cefiderocol, cefoxitin and doripenem) which would be acceptable in regions outside the UK beyond that listed in the Summary of Product Characteristics.This review has not been registered under PROSPERO.

Does comorbidity index predict OPAT readmission?

Objectives

To determine if the Charlson comorbidity index (CCI) is an accurate predictor of unplanned readmissions for patients using outpatient parenteral antimicrobial therapy (OPAT) services.

Methods

Retrospective analysis of patients >16 years of age who had received OPAT at Lancashire Teaching Hospitals between 2019 and 2021. The number of unplanned hospitalizations was measured and categorized as OPAT related or non-OPAT related. The CCI for each patient group was calculated using an online tool, and logistic regression was used to assess the association between risk factors and risk of being readmitted.

Results

The cohort consisted of 741 patients. Unplanned readmission was seen in 112 patients (15.1%). The mean CCI score for patients with OPAT-related readmissions was 4.22, 0.92 higher than the mean for patients who were not readmitted (3.30). The mean CCI score for patients with non-OPAT-related readmissions was higher still at 4.89. The logistic regression showed that increased CCI, age, male gender and home location compared with clinic were associated with increased odds of readmission, although these effects did not meet statistical significance.

Conclusions

These results suggest that a higher CCI score is associated with a non-statistically significant increased risk of unplanned hospitalization. We concluded that the CCI may therefore be used in future decision-making regarding the acceptance of patients to OPAT and requires further investigation.

Early switch from intravenous to oral antibiotic treatment in bone and joint infections

OBJECTIVES

The timing of the switch from intravenous (i.v.) to oral antibiotic therapy for orthopaedic bone and joint infections (BJIs) is debated. In this narrative article, we discuss the evidence for and against an early switch in BJIs.

DATA SOURCES

We performed a PubMed and internet search investigating the association between the duration of i.v. treatment for BJI and remission of infection among adult orthopaedic patients.

CONTENT

Among eight randomized controlled trials and multiple retrospective studies, we failed to find any minimal duration of postsurgical i.v. therapy associated with clinical outcomes. We did not find scientific data to support the prolonged use of i.v. therapy or to inform a minimal duration of i.v.

THERAPY

Growing evidence supports the safety of an early switch to oral medications once the patient is clinically stable.

IMPLICATIONS

After surgery for BJI, a switch to oral antibiotics within a few days is reasonable in most cases. We recommend making the decision on the time point based on clinical criteria and in an interdisciplinary team at the bedside.

Implementation of the national antimicrobial stewardship competencies for UK undergraduate healthcare professional education within undergraduate pharmacy programmes: a survey of UK schools of pharmacy

BACKGROUND

Pharmacists play a key role in antimicrobial stewardship (AMS). Consensus-based national AMS competencies for undergraduate healthcare professionals in the UK reflect the increasing emphasis on competency-based healthcare professional education. However, the extent to which these are included within undergraduate pharmacy education programmes in the UK is unknown.

OBJECTIVES

To explore which of the AMS competencies are delivered, including when and at which level, within UK undergraduate MPharm programmes.

METHODS

A cross-sectional online questionnaire captured the level of study of the MPharm programme in which each competency was taught, the method of delivery and assessment of AMS education, and examples of student feedback.

RESULTS

Ten institutions completed the survey (33% response rate). No institution reported covering all 54 AMS competencies and 5 of these were taught at half or fewer of the institutions. Key gaps were identified around taking samples, communication, outpatient parenteral antimicrobial therapy and surgical prophylaxis. The minimum time dedicated to AMS teaching differed between institutions (range 9-119 h), teaching was generally through didactic methods, and assessment was generally through knowledge recall and objective structured clinical examinations. Feedback from students suggests they find AMS and antimicrobial resistance (AMR) to be complex yet important topics.

CONCLUSIONS

UK schools of pharmacy should utilize the competency framework to identify gaps in their AMS, AMR and infection teaching. To prepare newly qualified pharmacists to be effective at delivering AMS and prescribing antimicrobials, schools of pharmacy should utilize more simulated environments and clinical placements for education and assessment of AMS.

Real-Life Experience of Continuously Infused Ceftolozane/Tazobactam in Patients with Bronchiectasis and Multidrug-Resistant Pseudomonas aeruginosa Infection in the Outpatient Setting

(1) Background: Ceftolozane/tazobactam (C/T) is a novel β-lactam/β-lactamase inhibitor with excellent activity against the multidrug-resistant (MDR) P. aeruginosa. Continuous infusion (CI) dosing allows the optimization of pharmacokinetic and pharmacodynamic (PK/PD) properties of β-lactam antibiotics and may support patients' treatment as outpatients. (2) Methods: Adult patients receiving their entire course of C/T as a CI in the outpatient setting were retrospectively included in the study. The primary outcome evaluated was clinical resolution. The secondary outcomes evaluated were PK/PD target attainment (ƒT > 4 × MIC) and microbiologic clearance at the end of treatment. Therapeutic drug monitoring to assess C/T concentration was performed. (3) Results: Three patients were enrolled in the study and received 9 g of C/T in CI every 24 h. One patient received an additional course of antimicrobial therapy due to disease exacerbation six months after initial treatment, accounting for four evaluated treatments. The primary outcome was achieved in 3/4 treatments and the secondary outcome was achieved in 4/4 and 3/3, respectively. In all patients, free ceftolozane concentrations were >10 times higher than the EUCAST breakpoint (4 mg/L). (4) Conclusions: Elastomeric infusion of C/T delivered in CI can be an effective and convenient way to treat acute diseases caused by MDR-P. aeruginosa, avoid hospital admission, and contribute to infection control strategies. Despite the small number of enrolled patients, clinical and microbiological results support this strategy.

A Bundle of the Top 10 OPAT Publications in 2022

Outpatient parenteral antimicrobial therapy (OPAT) has become more common in clinical settings. Correspondingly, OPAT-related publications have also increased; the objective of this article was to summarize clinically meaningful OPAT-related publications in 2022. Seventy-five articles were initially identified, with 54 being scored. The top 20 OPAT articles published in 2022 were reviewed by a group of multidisciplinary OPAT clinicians. This article provides a summary of the "top 10" OPAT publications of 2022.

Exploring the advancements of Australian OPAT

Outpatient parenteral antimicrobial therapy (OPAT) in Australia has evolved from modest beginnings to a well-established health service with proven benefits in patient outcomes. This is a comprehensive review of the current state of art Australian OPAT with vignettes of the types of OPAT models of care, antimicrobial prescribing and antimicrobial use. In addition, we highlight the similarities and differences between OPAT to other countries and describe Australian OPAT experiences with COVID-19 and paediatrics. Australian OPAT continues to advance with OPAT antifungals, novel treatment options and upcoming high-impact research.

Current Practices and Opportunities for Outpatient Parenteral Antimicrobial Therapy in Hospitals: A National Cross-Sectional Survey

This nationwide study assessed how outpatient parenteral antimicrobial therapy (OPAT) is organised by Dutch acute care hospitals, the barriers experienced, and how an OPAT program affects the way hospitals organised OPAT care. We systematically developed and administered a survey to all 71 Dutch acute care hospitals between November 2021 and February 2022. Analyses were primarily descriptive and included a comparison between hospitals with and without an OPAT program. Sixty of the 71 hospitals (84.5%) responded. Fifty-five (91.7%) performed OPAT, with a median number of 20.8 (interquartile range [IQR] 10.3-29.7) patients per 100 hospital beds per year. Of these 55 hospitals, 31 (56.4%) had selection criteria for OPAT and 34 (61.8%) had a protocol for laboratory follow-up. Sixteen hospitals (29.1%) offered self-administered OPAT (S-OPAT), with a median percentage of 5.0% of patients (IQR: 2.3%-10.0%) actually performing self-administration. Twenty-five hospitals (45.5%) had an OPAT-related outcome registration. The presence of an OPAT program (22 hospitals, 40.0%) was significantly associated with aspects of well-organised OPAT care. The most commonly experienced barriers to OPAT implementation were a lack of financial, administrative, and IT support and insufficient time of healthcare staff. Concluding, hospital-initiated OPAT is widely available in the Netherlands, but various aspects of well-organised OPAT care can be improved. Implementation of a team-based OPAT program can contribute to such improvements. The observed variation provides leads for further scientific research, guidelines, and practical implementation programs.

Activity of ertapenem/zidebactam (WCK 6777) against problem Enterobacterales

Background

Secondary healthcare will remain pressured for some years, both because SARS-CoV-2 will circulate as a nosocomial pathogen, and owing to backlogs of patients awaiting delayed elective procedures. These stresses will drive the use of Outpatient Parenteral Antibiotic Therapy (OPAT), which will need to cover increasingly resistant Gram-negative opportunists. We evaluated the activity of ertapenem/zidebactam, proposed for 2 + 2 g q24h administration.

Materials and methods

MICs were determined, by BSAC agar dilution, for 1632 Enterobacterales submitted to the UK national reference laboratory for investigation of antimicrobial resistance.

Results

Over 90% of Escherichia coli with AmpC, ESBLs, KPC, metallo- or OXA-48 carbapenemases were inhibited by ertapenem/zidebactam 1:1 at ertapenem’s current 0.5 mg/L breakpoint. For other major Enterobacterales, the proportions inhibited by ertapenem/zidebactam 1:1 at 0.5 mg/L were mostly 65% to 90% but were lower for Klebsiella pneumoniae/oxytoca with metallo- or OXA-48 β-lactamases. However, animal studies support an 8 mg/L breakpoint for ertapenem/zidebactam, based on a shortened T_>MIC being needed compared with ertapenem alone. On this basis ertapenem/zidebactam would count as active against 90%–100% of isolates in all groups except K. pneumoniae/oxytoca with MBLs (±OXA-48), where MICs and percent susceptibility vary substantially even with inocula within the BSAC acceptable range.

Conclusions

Ertapenem/zidebactam has a proposed once-daily regimen well suited to OPAT. Even on highly conservative breakpoint projections, it has potential against MDR E. coli, including metallo-carbapenemase producers. If trial data sustain the 8 mg/L breakpoint indicated by animal experiments, its potential will extend widely across infections due to ESBL-, AmpC- and carbapenemase-producing Enterobacterales.